Purified air is needed for a variety of applications, such as zero setting for analyzers, oxidizer gas for analyzers, and dilution air for emissions analysis. Increasingly lower standards for the quality of “normal” air requires improved quality “zero,” oxidizer, and dilution air.
FIG. 1 is a depiction of a generic description of prior art air purification. Purified air is currently available mainly in limited quantities in bottled gas form from companies that supply both pure oxygen and nitrogen as well. The process of purifying air, as opposed to purifying a single type of gas, is usually far more expensive and energy intensive because the air has to be broken down into the gas components of nitrogen and oxygen, each gas separately purified, and then recombined in the bottle gas form. Such a system is depicted in prior art FIG. 2 and creates a high energy and monetary cost for purified air. FIG. 3 represents prior art a method of pressure swing adsorption and will be detailed below. FIG. 4 represents the membrane filter method, and is also well known to those skilled in the art. Both of the methods depicted in FIGS. 3 and 4 can severely affect the nitrogen and oxygen ratios of purified air resulting in unusable purified air for the purposes mentioned above.
For example, U.S. Pat. No. 5,931,022 to Deng, et. al. and assigned to BOC of Murray Hill, N.J., and incorporated herein by reference, teaches a way to regenerate the alumina thermal purification units by keeping them 180 degrees in phase. However, this system is limited because it only teaches how to remove carbon dioxide from air. This system also teaches the pressure swing adsorption method of impurity remove (herein PSA). As stated above, PSA has the drawback that the more aggressively the carbon dioxide is removed from the air to be purified, the more the air is at risk for a significant reduction in nitrogen levels. The reduction in nitrogen levels changes the nitrogen-to-oxygen ratio and makes the resulting purified air less suitable for the uses of calibration, analysis, and dilution. The details of the actual PSA method are well known to those skilled in the area of gas purification and do not need to be detailed here.
What is needed is a system in which purified air is created from normal air without the cost and energy expense of breaking the air into its component gases. What is also needed is an air purification system in which the oxygen and nitrogen ratios are maintained in order to provide purified air which is usable for calibration and other purposes.
Furthermore, it is desirable and cost effective to have such a purification system in which the purification units or adsorbers can regenerate themselves automatically, eliminating the need to replace the purification units.
Additionally, it is desirable to have an ability to regenerate the adsorption units without having to remove the units to permit the uninterrupted operation of the air purifiers. Finally, it is desirable to treat the air before purification, such that the purification is performed more efficiently and the life of the adsorption units and the oxygen catalyst units are extended.